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<TITLE>The E-Mail Virus</TITLE>
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<H1 ALIGN=CENTER>The E-Mail Virus</H1>

<P>Every once in a while I get something over the internet warning me about e-mail 
messages with particular subject headings. One is led to believe that cataclysmic 
things will happen to one's hard drive if one tries to read such messages. I find 
that it would be next to impossible for this to happen.

<P>Files in a computer can be treated as either data or executable programs. They 
actually enter the central processing unit from different paths depending on their 
purpose. Executable programs do something: data is information.

<P>A virus can only be active (do something) if it is a piece of an executable; if 
however it is in file that is treated only as data, it can do no harm. 

<P>In almost all cases your e-mail program will treat your messages as data. Now 
in addition to a main message, you may get attachments. Some of these may be out-
and-out executables, and some - like a word processing file - may contain macros 
that could launch a virus; but reading the main message would not run these or any 
other executable programs that did not exist on the system before the message 
arrived.

<P>There is another issue. In order for a virus to effectively spread through the 
internet, it should be able to run on the computers it encounters; however each 
type of computer requires a different kind of executable. Not only do you have 
Macs and PCs but you would also get Sun workstations, Hewlett-Packard mainframes, 
Vax machines, Crays, and so on. To infect all of these systems, a virus would need 
to have a piece of executable taylored for each one; furthermore the virus creator 
would have to have a detailed understanding of each computer type in order to 
cause similar damage on all systems.

<P>What we have here is not a computer virus but a computer rumor: it is the 
original message that provides the "warning" - propagated not by the innards of a 
computer but by the users. If you have forwarded such a rumor or know someone else 
who has, please send a message not to spread these things further.

<P>In saying this I acknowledge that there are some crafty people out there. If 
you ever do get a virus by JUST reading an e-mail message, I would be most 
interested in learning about it. Once you have returned your system to normal, 
please write to me at landrum@mail.utexas.edu .
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<CENTER>Robert G. Landrum<BR>
December 16, 1996</CENTER><BR>

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